Atherosclerosis is a disease of the circulatory system characterized by fatty or calcified deposits or fibrous tissue growth which occlude blood vessels. It is a leading cause of death by disease in the United States. The atherosclerotic stenoses or blockages tend to reduce cross sectional area of the blood vessels thereby impeding blood circulation. In severe cases, the entire vessel may be significantly narrowed or blocked by the deposits, thereby causing or contributing angina pectoris, stroke, myocardial infarction and other conditions.
Atherosclerosis may be treated through coronary by-pass surgery wherein an autogenous vein or synthetic graft is used to by-pass the diseased artery. Of course, this technique involves a major surgical operation at substantial risk and expense to the patient, and a significant recovery period.
Balloon angioplasty is another method for treating atherosclerosis. With this technique a balloon catheter is routed through the artery to the site of the blockage. Once in position, the balloon is inflated to compress or displace the blockage. Balloon angioplasty requires only local anesthesia and avoids many of the risks, expenses and prolonged recovery associated with by-pass surgery. However, if the blockage or stenosis is asymmetrical or fully closed, this technique may be unavailable or ineffective. Similarly, balloon angioplasty may not work with highly calcified or fibrous blockages.
Various atherectomy catheters having mechanical cutting edges for cutting blockages have also been proposed. While these devices have met with varying degrees of success in principle and application, certain disadvantages remain. If a single cutting device is unable to remove a wide range of blockages, then a series of cutting devices of varying size and perhaps shape must be employed. This requires the surgeon to repeatedly locate the blockage, guide a first cutting device to it, perform the cutting operation, withdraw the cutting device from the patient, replace it with the next size cutting device in sequence--and then repeat the operation for as many times as is necessary. Repeatedly inserting and removing the cutting devices from the patient is time consuming and increases risk to the patient. In addition, with all cutting devices there is a need to prevent inadvertent cutting into or through healthy arterial walls.
Accordingly, it is an object of the invention to provide an improved atherectomy catheter. It is a further object of the invention to provide an improved stent for use in blood vessels having undergone blockage removal procedures.